SharedPreferences

    public class MyActivity extends AppCompatActivity implements View.OnClickListener {
     
    public static SharedPreferences settings;         // get
    private static SharedPreferences.Editor editor; // put
     
     protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_login);
     
            settings = getSharedPreferences("mySavedStuff", MODE_PRIVATE);
            editor = settings.edit();
     
            if (settings.contains("USERNAME")){
                login();
            }
            btn = (Button) findViewById(R.id.btn);
            btn.setOnClickListener(this);
        }
     
        @Override
        public void onClick(View v) {
            EditText username = (EditText) findViewById(R.id.usernameEditText);
            String user = username.getText().toString().trim();
            if (validate(user)){
                editor.putString("USERNAME", user);
                editor.putInt("age", 30);
                editor.putBoolean("isMale", true);
                editor.commit();    // DON'T FORGET THIS LINE!!!
                login();
            }
        }
     
        private void login(){
            Intent intent = new Intent(this, ListActivity.class);
            startActivity(intent);
        }
     
        private boolean validate(String str){
            if (str.isEmpty()){
                return false;
            }
            return true;
        }
    }
    //////////////////////////////////////////////
    //SharedPreferences Support:
     
    .getInt("data", 1); //get int
    .putInt(dara", 1); //put int
    .remove("setings to remove"); //delete using the key name
    .clear(); //delete all SharedPreferences keys
     
    .apply(); // like commit() but run in different thread (faster) !